Voters in north-central Massachusetts will cast ballots Tuesday in one of the cycle’s most crowded primaries. Democratic Rep. Niki Tsongas is retiring after five full terms, creating a free-for-all for the 3rd District, the state’s only open seat this year.

The ten Democrats running include the first openly transgender person to run for Congress in Massachusetts, two candidates who immigrated to the United States as children, and a former ambassador whose experience as a gay diplomat was chronicled in a Danish television documentary. Winning the primary would be tantamount to victory in the heavily Democratic seat that Hillary Clinton carried by 23 points in 2016.